Method for determining uplink transmission power in a network including a plurality of cells, and apparatus therefor

ABSTRACT

Disclosed is a method for determining uplink transmission power in a network including a plurality of cells, and an apparatus therefor. The method for a terminal to determine uplink transmission power in a network including a plurality of cells may comprise the following steps: receiving information including values of path-loss compensation factors set for each of the plurality of cells; determining uplink transmission power using the value of the path-loss compensation factor corresponding to the cell, from among the plurality of cells, in which the terminal is currently located; and a step of transmitting an uplink signal using the determined transmission power.

TECHNICAL FIELD

The present invention relates to a wireless communication, and moreparticularly, to a method of determining uplink transmit power in anetwork including a plurality of cells and an apparatus therefor.

BACKGROUND ART

3GPP LTE (3^(rd) generation partnership project long term evolutionhereinafter abbreviated LTE) communication system is schematicallyexplained as an example of a wireless communication system to which thepresent invention is applicable.

FIG. 1 is a schematic diagram of E-UMTS network structure as one exampleof a wireless communication system.

E-UMTS (evolved universal mobile telecommunications system) is a systemevolved from a conventional UMTS (universal mobile telecommunicationssystem). Currently, basic standardization works for the E-UMTS are inprogress by 3GPP. E-UMTS is called LTE system in general. Detailedcontents for the technical specifications of UMTS and E-UMTS refers torelease 7 and release 8 of “3^(rd) generation partnership project;technical specification group radio access network”, respectively.

Referring to FIG. 1, E-UMTS includes a user equipment (UE), a basestation (BS), and an access gateway (hereinafter abbreviated AG)connected to an external network in a manner of being situated at theend of a network (E-UTRAN). The eNode B may be able to simultaneouslytransmit multi data streams for a broadcast service, a multicast serviceand/or a unicast service.

One base station contains at least one cell. The cell provides adownlink transmission service or an uplink transmission service to aplurality of user equipments by being set to one of 1.25 MHz, 2.5 MHz, 5MHz, 10 MHz, 15 MHz, and 20 MHz of bandwidths. Different cells can beconfigured to provide corresponding bandwidths, respectively. A basestation controls data transmissions/receptions to/from a plurality ofthe user equipments. For a downlink (hereinafter abbreviated DL) data,the base station informs a corresponding user equipment oftime/frequency region on which data is transmitted, coding, data size,HARQ (hybrid automatic repeat and request) related information and thelike by transmitting DL scheduling information. And, for an uplink(hereinafter abbreviated UL) data, the base station informs acorresponding user equipment of time/frequency region usable by thecorresponding user equipment, coding, data size, HARQ-relatedinformation and the like by transmitting UL scheduling information tothe corresponding user equipment. Interfaces for user-traffictransmission or control traffic transmission may be used between basestations. A core network (CN) consists of an AG (access gateway) and anetwork node for user registration of a user equipment and the like. TheAG manages a mobility of the user equipment by a unit of TA (trackingarea) consisting of a plurality of cells.

Wireless communication technologies have been developed up to LTE basedon WCDMA (wideband code division multiple access). Yet, the ongoingdemands and expectations of users and service providers are consistentlyincreasing. Moreover, since different kinds of radio access technologiesare continuously developed, a new technological evolution is required tohave a future competitiveness. Cost reduction per bit, serviceavailability increase, flexible frequency band use, simplestructure/open interface and reasonable power consumption of a userequipment and the like are required for the future competitiveness.

Recently, ongoing standardization of the next technology of LTE isperformed by 3GPP. Such technology shall be named LTE-A in the presentspecification. One of main differences between LTE system and LTE-Asystem may include a system bandwidth difference and an adoption of arelay node.

The goal of LTE-A system is to support maximum 100 MHz wideband. To thisend, LTE-A system uses carrier aggregation or bandwidth aggregation toachieve the wideband using a plurality of frequency blocks.

According to the carrier aggregation, pluralities of frequency blocksare used as one wide logical frequency band to use wider frequency band.A bandwidth of each frequency block may be defined based on a bandwidthof a system block used by LTE system. Each frequency block istransmitted using a component carrier.

DISCLOSURE OF THE INVENTION Technical Task

A technical task intended to achieve by the present invention is toprovide a method of determining uplink transmit power, which isdetermined by a user equipment in a network including a plurality ofcells.

Another technical task intended to achieve by the present invention isto provide a user equipment determining uplink transmit power in anetwork including a plurality of cells.

Technical tasks obtainable from the present invention are non-limitedthe above mentioned technical tasks. And, other unmentioned technicaltasks can be clearly understood from the following description by thosehaving ordinary skill in the technical field to which the presentinvention pertains.

Technical Solution

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, accordingto one embodiment, a method of determining an uplink transmit power by auser equipment in a network including a plurality of cells, includesreceiving information including a pathloss compensation factor value setfor each of a plurality of the cells, determining an uplink transmitpower using the pathloss compensation factor value corresponding to acell at which the user equipment is currently positioned among each ofthe plurality of the cells, and transmitting an uplink signal using thedetermined transmit power. A plurality of the cells includes aheterogeneous cell and the set pathloss compensation factor value may bedifferent from each other between the heterogeneous cells. The pathlosscompensation factor value set for each of the cells may be configured inaccordance with the cells based on a resource allocation pattern foreach of the cells. The pathloss compensation factor value set for eachof the cells may be configured with a specific time unit in each of thecells. The specific time unit includes a frame, a subframe, or a symbolunit. The uplink transmit power may correspond to a transmit power tofor a PUSCH (physical uplink shared channel) transmission and thepathloss compensation factor value set for each of the plurality of thecells may be set further based on whether each of the cells correspondsto an isolated cell.

The method may further include receiving information on the resourceallocation pattern for each of the cells. The resource allocationpattern for each of the cells may include at least one an ABS (almostblanking subframe) assignment pattern information for each of the cells,information on PUSCH (physical uplink shared channel) transmissionresource for each of the cells, and information on PUCCH transmissionresource for each of the cells.

To further achieve these and other advantages and in accordance with thepurpose of the present invention, according to a different embodiment, auser equipment for determining an uplink transmit power in a networkincluding a plurality of cells includes a receiver configured to receiveinformation including a pathloss compensation factor value set for eachof a plurality of the cells, a processor configured to determine anuplink transmit power using the pathloss compensation factor valuecorresponding to a cell at which the user equipment is currentlypositioned among each of a plurality of the cells, and a transmitterconfigured to transmit an uplink signal using the determined transmitpower. The pathloss compensation factor value set for each of the cellsmay be configured in accordance with the cells based on a resourceallocation pattern for each of the cells.

The receiver is configured to further receive information on theresource allocation pattern for each of the cells and the resourceallocation pattern for each of the cells may include at least one an ABS(almost blanking subframe) assignment pattern information for each ofthe cells, PUSCH (physical uplink shared channel) transmission resourceaccording to the cells, and information on PUCCH transmission resourcefor each of the cells.

Advantageous Effects

According to various embodiments, performance of a pico cell, an RRH, afemto cell can be maximized in a situation that an eICIC is taken intoaccount.

Effects obtainable from the present invention may be non-limited by theabove mentioned effect. And, other unmentioned effects can be clearlyunderstood from the following description by those having ordinary skillin the technical field to which the present invention pertains.

DESCRIPTION OF DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention.

FIG. 1 is a schematic diagram of E-UMTS network structure as one exampleof a wireless communication system;

FIG. 2 is a block diagram for configurations of a base station 205 and auser equipment 210 in a wireless communication system 200;

FIG. 3 is a diagram for one example of a radio frame structure used in3GPP LTE/LTE-A system as one example of a wireless communication system;

FIG. 4 is a diagram for an example of a resource grid of a downlink slotof 3GPP LTE/LTE-A system as one example of a wireless communicationsystem;

FIG. 5 is a diagram for a downlink subframe structure of 3GPP LTE systemas one example of a wireless communication system;

FIG. 6 is a diagram for an uplink subframe structure of 3GPP LTE systemas one example of a wireless communication system;

FIG. 7 is a diagram for an example of a carrier aggregation (CA)communication system;

FIG. 8 is a diagram for an example of an inter-cell interferencesituation;

FIG. 9 is a diagram for an example of an inter-cell interferencesituation in a heterogeneous network environment;

FIG. 10 is an exemplary diagram for explaining a downlink eICIC solutionin a configuration depicted in FIG. 9;

FIG. 11 is an exemplary diagram for explaining an uplink eICIC solutionin a configuration depicted in FIG. 9;

FIG. 12 is a different exemplary diagram for explaining an uplink eICICsolution in a configuration depicted in FIG. 9.

BEST MODE Mode for Invention

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. In the following detailed description of the inventionincludes details to help the full understanding of the presentinvention. Yet, it is apparent to those skilled in the art that thepresent invention can be implemented without these details. Forinstance, although the following descriptions are made in detail on theassumption that a mobile communication system includes 3GPP LTE/LTE-Asystem, they are applicable to other random mobile communication systemsexcept unique features of 3GPP LTE/LTE-A system.

Occasionally, to prevent the present invention from getting vaguer,structures and/or devices known to the public are skipped or can berepresented as block diagrams centering on the core functions of thestructures and/or devices. Wherever possible, the same reference numberswill be used throughout the drawings to refer to the same or like parts.

Besides, in the following description, assume that a terminal is acommon name of such a mobile or fixed user stage device as a userequipment (UE), a mobile station (MS), an advanced mobile station (AMS),and the like. And, assume that a base station is a common name of such arandom node of a network stage communicating with a terminal as a NodeB, an eNode B, a base station (BS), an access point (AP) and the like.

In a mobile communication system, a user equipment may be able toreceive information from a base station in downlink and transmit theinformation to the base station in uplink. The informations transmittedor received by user equipment may include data and various controlinformations. And, various kinds of physical channels may exist inaccordance with types and usages of the informations transmitted orreceived by the user equipment.

FIG. 2 is a block diagram for configurations of a base station 205 anduser equipment 210 in a wireless communication system 200.

Although one base station 205 and one user equipment 210 are shown inthe drawing to schematically represent a wireless communication system200, the wireless communication system 200 may include at least one basestation and/or at least one user equipment.

Referring to FIG. 2, a base station 205 may include a transmitted (Tx)data processor 215, a symbol modulator 220, a transmitter 225, atransceiving antenna 230, a processor 280, a memory 285, a receiver 290,a symbol demodulator 295 and a received data processor 297. And, a userequipment 210 may include a transmitted (Tx) data processor 265, asymbol modulator 270, a transmitter 275, a transceiving antenna 235, aprocessor 255, a memory 260, a receiver 240, a symbol demodulator 255and a received data processor 250. Although it is depicted that the basestation 205 and the user equipment 210 include one antenna 230/235,respectively in the drawing, each of the base station 205 and the userequipment 210 includes a plurality of antennas. Hence, the base station205 and the user equipment 210 according to the present inventionsupport an MIMO (multiple input multiple output) system. And, the basestation 205 according to the present invention may support both aSU-MIMO (single user-MIMO) and an MU-MIMO (multi user-MIMO) scheme.

In downlink, the transmitted data processor 215 receives traffic data,formats the received traffic data, codes the traffic data, interleavesthe coded traffic data, modulates (or symbol maps) the interleaved data,and then provides modulated symbols (‘data symbols’). The symbolmodulator 220 provides a stream of symbols by receiving and processingthe data symbols and pilot symbols.

The symbol modulator 220 multiplexes the data symbols and the pilotsymbols together and then transmits the multiplexed symbols to thetransmitter 225. In doing so, each of the transmitted symbols mayinclude the data symbol, the pilot symbol or a signal value of zero(i.e., null). In each of symbol durations, the pilot symbols may becontiguously transmitted. In doing so, the pilot symbols may includesymbols of frequency division multiplexing (FDM), orthogonal frequencydivision multiplexing (OFDM), time division multiplexing (TDM), or codedivision multiplexing (CDM).

The transmitter 225 receives the stream of the symbols, converts thereceived stream to at least one or more analog signals, additionallyadjusts the analog signals (e.g., amplification, filtering, frequencyupconverting, etc.), and then generates a downlink signal suitable for atransmission on a radio channel. Subsequently, the downlink signal istransmitted to the user equipment via the transmitting antenna 230.

In the configuration of the user equipment 210, the receiving antenna235 receives the downlink signal from the base station and then providesthe received signal to the receiver 240. The receiver 240 adjusts thereceived signal (e.g., filtering, amplification and frequencydownconverting), digitizes the adjusted signal, and then obtainssamples. The symbol demodulator 245 demodulates the received pilotsymbols and then provides them to the processor 255 for channelestimation.

The symbol demodulator 245 receives a frequency response estimated valuefor downlink from the processor 255, obtains data symbol estimatedvalues (i.e., estimated values of the transmitted data symbols) byperforming data modulation on the received data symbols, and thenprovides the data symbol estimated values to the received (Rx) dataprocessor 250. The received data processor 250 reconstructs thetransmitted traffic data by performing demodulation (i.e., symboldemapping, deinterleaving and decoding) on the data symbol estimatedvalues.

The processing by the symbol demodulator 245 and the processing by thereceived data processor 250 are complementary to the processing by thesymbol modulator 220 and the processing by the transmitted dataprocessor 215 in the base station 205, respectively.

Regarding the user equipment 210 in uplink, the transmitted dataprocessor 265 provides data symbols by processing the traffic data. Thesymbol modulator 270 provides a stream of symbols to the transmitter 275by receiving the data symbols, multiplexing the received data symbols,and then performing modulation on the multiplexed symbols. Thetransmitter 275 generates an uplink signal by receiving the stream ofthe symbols and then, processing the received stream. The generateduplink signal is then transmitted to the base station 205 via thetransmitting antenna 235.

In the base station 205, the uplink signal is received from the userequipment 210 via the receiving antenna 230. The receiver 290 obtainssamples by processing the received uplink signal. Subsequently, thesymbol demodulator 295 provides pilot symbols received in uplink and adata symbol estimated value by processing the obtained samples. Thereceived data processor 297 reconstructs the traffic data transmittedfrom the user equipment 210 by processing the data symbol estimatedvalue.

The processor 255/280 of the user equipment/base station 210/205 directsoperations (e.g., control, adjustment, management, etc.) of the userequipment/base station 210/205. The processor 255/280 may be connectedto the memory unit 260/285 configured to store program codes and data.The memory 260/285 is connected to the processor 255/280 to storeoperating systems, applications and general files.

The processor 255/280 may be called one of a controller, amicrocontroller, a microprocessor, a microcomputer and the like. And,the processor 255/280 may be implemented using hardware, firmware,software and/or any combinations thereof. In the implementation byhardware, the processor 255/280 may be provided with one of ASICs(application specific integrated circuits), DSPs (digital signalprocessors), DSPDs (digital signal processing devices), PLDs(programmable logic devices), FPGAs (field programmable gate arrays),and the like.

Meanwhile, in case of implementing the embodiments of the presentinvention using firmware or software, the firmware or software may beconfigured to include modules, procedures, and/or functions forperforming the above-explained functions or operations of the presentinvention. And, the firmware or software configured to implement thepresent invention is loaded in the processor 255/280 or saved in thememory 260/285 to be driven by the processor 255/280.

Layers of a radio protocol between a user equipment and a base stationmay be classified into 1^(st) layer L1, 2^(nd) layer L2 and 3^(rd) layerL3 based on 3 lower layers of OSI (open system interconnection) modelwell known to communication systems. A physical layer belongs to the1^(st) layer and provides an information transfer service via a physicalchannel. RRC (radio resource control) layer belongs to the 3^(rd) layerand provides control radio resources between UE and network. A userequipment and a base station may be able to exchange RRC messages witheach other via a radio communication network using RRC layers.

FIG. 3 is a diagram for one example of a radio frame structure used in3GPP LTE/LTE-A system as one example of a wireless communication system.

In a cellular OFDM radio packet communication system, UL/DL(uplink/downlink) data packet transmission is performed by a unit ofsubframe. And, one subframe is defined as a predetermined time intervalincluding a plurality of OFDM symbols. In the 3GPP LTE standard, atype-1 radio frame structure applicable to FDD (frequency divisionduplex) and a type-2 radio frame structure applicable to TDD (timedivision duplex) are supported.

FIG. 3 (a) is a diagram for a structure of a downlink radio frame oftype 1. A DL (downlink) radio frame includes 10 subframes. Each of thesubframes includes 2 slots. And, a time taken to transmit one subframeis defined as a transmission time interval (hereinafter abbreviatedTTI). For instance, one subframe may have a length of 1 ms and one slotmay have a length of 0.5 ms. One slot may include a plurality of OFDMsymbols in time domain and may include a plurality of resource blocks(RBs) in frequency domain. Since 3GPP LTE system uses OFDM in downlink,OFDM symbol is provided to indicate one symbol interval. The OFDM symbolmay be named SC-FDMA symbol or symbol interval. Resource block (RB) is aresource allocation unit and may include a plurality of contiguoussubcarriers in one slot.

The number of OFDM symbols included in one slot may vary in accordancewith a configuration of CP. The CP may be categorized into an extendedCP and a normal CP. For instance, in case that OFDM symbols areconfigured by the normal CP, the number of OFDM symbols included in oneslot may be 7. In case that OFDM symbols are configured by the extendedCP, since a length of one OFDM symbol increases, the number of OFDMsymbols included in one slot may be smaller than that of the case of thenormal CP. In case of the extended CP, for instance, the number of OFDMsymbols included in one slot may be 6. If a channel status is unstable(e.g., a UE is moving at high speed), it may be able to use the extendedCP to further reduce the inter-symbol interference.

When a normal CP is used, since one slot includes 7 OFDM symbols, onesubframe includes 14 OFDM symbols. In this case, first maximum 3 OFDMsymbols of each subframe may be allocated to PDCCH (physical downlinkcontrol channel), while the rest of the OFDM symbols are allocated toPDSCH (physical downlink shared channel).

FIG. 3 (b) is a diagram for a structure of a downlink radio frame oftype 2. A type-2 radio frame includes 2 half frames. Each of the halfframe includes 5 subframes, a DwPTS (downlink pilot time slot), a GP(guard period), and an UpPTS (uplink pilot time slot). Each of thesubframes includes 2 slots. The DwPTS is used for initial cell search,synchronization, or a channel estimation in a user equipment. The UpPTSis used for channel estimation of a base station and matching atransmission synchronization of a user equipment. The guard period is aperiod for eliminating interference generated in uplink due tomulti-path delay of a downlink signal between uplink and downlink.

The above-described structures of the radio frame are exemplary only.And, the number of subframes included in a radio frame, the number ofslots included in the subframe and the number of symbols included in theslot may be modified in various ways.

FIG. 4 is a diagram for an example of a resource grid of a downlink slotof 3GPP LTE/LTE-A system as one example of a wireless communicationsystem.

Referring to FIG. 4, one downlink (DL) slot may include a plurality ofOFDM symbols in time domain. In particular, one DL slot includes 7 (6)OFDM symbols and one resource block (RB) may include 12 subcarriers infrequency domain. Each element on a resource grid is called a resourceelement (hereinafter abbreviated RE). One resource block includes12×7(6) resource elements. The number N_(RB) of resource blocks includedin a DL slot may depend on a DL transmission bandwidth. And, thestructure of an uplink (UL) slot may be identical to that of the DL slotand an OFDM symbol is replaced with an SC-FDMA symbol.

FIG. 5 is a diagram for a downlink subframe structure of 3GPP LTE systemas one example of a wireless communication system.

Referring to FIG. 5, maximum 3(4) fore OFDM symbols of the first slotwithin a DL subframe correspond to a control region for allocatingcontrol channels thereto and the rest of the OFDM symbols correspond toa data region for allocating PDSCH (physical downlink shared channel)thereto. DL (downlink) control channels used in LTE system includePCFICH (physical control format indicator channel), PDCCH (physicaldownlink control channel), PHICH (physical hybrid-ARQ indicatorchannel), etc. The PCFICH carried on a first OFDM symbol of a subframecarries the information on the number of OFDM symbols used for thetransmission of control channels within the subframe. The PHICH carriesHARQ ACK/NACK (hybrid automatic repeat request acknowledgement/negativeacknowledgement) signal in response to an UL transmission.

Control information carried on PDCCH may be called downlink controlinformation (DCI: downlink control indicator). A DCI format is definedby a format of 0 for an uplink and the DCI format is defined by formatsof 1, 1A, 1B, 1C, 1D, 2, 2A, 3, 3A and the like for a downlink. The DCIformat may be able to selectively include a hopping flag, an RBassignment, an MCS (modulation coding scheme), an RV (redundancyversion), an NDI (new data indicator), a TPC (transmit power control), acyclic shift DM RS (demodulation reference signal), a CQI (channelquality information) request, a HARQ process number, a TPMI (transmittedprecoding matrix indicator), a PMI (precoding matrix indicator)confirmation and the like according to a usage.

PDCCH is able to carry a transmission format and resource allocationinformation of DL-SCH (downlink shared channel), a transmission formatand resource allocation information of UL-SCH (uplink shared channel),paging information on PCH (paging channel), system information onDL-SCH, resource allocation information of an upper layer controlmessage such as a random access response transmitted on PDSCH, atransmit power control command set for individual user equipments withina user equipment (UE) group, a transmit power control command,activation indication information of VoIP (voice over IP) and the like.A plurality of PDCCHs can be transmitted in a control region and a userequipment is able to monitor a plurality of the PDCCHs. PDCCH istransmitted on a aggregation of a plurality of contiguous controlchannel elements (CCEs). CCE is a logical assignment unit used toprovide PDCCH with a code rate in accordance with a state of a radiochannel. CCE corresponds to a plurality of REGs (resource elementgroups). A format of PDCCH and the number of bits of PDCCH aredetermined depending on the number of CCEs. A base station determinesPDCCH format in accordance with DCI to transmit to a user equipment andattaches CRC (cyclic redundancy check) to control information. The CRCis masked with an identifier (called RNTI (radio network temporaryidentifier)) in accordance with an owner or usage of PDCCH. If the PDCCHis provided for a specific user equipment, the CRC can be masked with anidentifier of the corresponding user equipment, i.e., C-RNTI (i.e.,Cell-RNTI). As a different example, if the PDCCH is provided for apaging message, the CRC can be masked with a paging identifier (e.g.,P-RNTI (Paging-RNTI)). If the PDCCH is provided for system information,and more particularly, for a system information block (SIB), the CRC canbe masked with a system information identifier (e.g., SI-RNTI (systeminformation-RNTI). If the PDCCH is provided for a random accessresponse, the CRC can be masked with RA-RNTI (random access-RNTI).

FIG. 6 is a diagram for an uplink subframe structure of 3GPP LTE systemas one example of a wireless communication system.

Referring to FIG. 6, an uplink subframe includes a plurality of slots(e.g., 2 slots). A slot may include a different number of SC-FDMAsymbols according to a length of CP. A UL subframe may be divided into acontrol region and a data region in frequency domain. The data regionincludes PUSCH and can be used for transmitting a data signal such as anaudio and the like. The control region includes PUCCH and can be usedfor transmitting UL control information (UCI). PUCCH includes an RB pairlocated at both ends of the data region on a frequency axis and hops ona slot boundary.

The PUCCH can be used for transmitting following control information.

-   -   SR (scheduling request): information used for making a request        for an uplink UL-SCH resource. This information is transmitted        using an OOK (on-off keying) scheme.    -   HARQ ACK/NACK: a response signal for a downlink data packet on        PDSCH. This information indicates whether the downlink data        packet is successively received. ACK/NACK 1 bit is transmitted        in response to a single downlink codeword (CW) and ACK/NACK 2        bits are transmitted in response to two downlink codewords.    -   CQI (channel quality indicator): feedback information on a        downlink channel. MIMO (multiple input multiple output)-related        feedback information includes an RI (rank indicator), a PMI        (precoding matrix indicator), a PTI (precoding type indicator),        and the like. 20 bits per subframe are used for this        information.

An amount of control information capable of being transmitted by a UE ina subframe can be determined according to the number of SC-FDMA symbolavailable to transmit the control information. The SC-FDMA available fortransmitting the control information means a remaining SC-FDMA symbolexcept an SC-FDMA symbol used for transmitting a reference signal (RS)in a subframe. In case of a subframe to which an SRS (sounding referencesignal) is configured thereto, a last SC-FDMA symbol of the subframe isexcluded as well. A reference signal is used to detect coherent ofPUCCH. PUCCH supports 7 formats depending on transmitted information.

Table 1 indicates a mapping relation between a PUCCH format and a UCI inLTE.

TABLE 1 PUCCH format UL control information (UCI) Format 1 SR(scheduling request) (un-modulated wave) Format 1a 1-bit HARQ ACK/NACK(SR existence/non-existence) Format 1b 2-bit HARQ ACK/NACK (SRexistence/non-existence) Format 2 CQI (20 coded bits) Format 2 CQI and1- or 2-bit HARQ ACK/NACK (20 bits) (only applied to extended CP) Format2a CQI and 1-bit HARQ ACK/NACK (20 + 1 coded bits) Format 2b CQI and2-bit HARQ ACK/NACK (20 + 2 coded bits)

FIG. 7 is a diagram for an example of a carrier aggregation (CA)communication system.

LTE-A system uses a carrier aggregation (or bandwidth aggregation)technique using a wider uplink/downlink bandwidth in a manner ofcollecting a plurality of uplink/downlink frequency bandwidths to use awider frequency bandwidth. Each of small frequency bandwidths istransmitted using a component carrier (CC). The component carrier can becomprehended as a carrier frequency (or, a center carrier, a centerfrequency) for a corresponding frequency block.

Each of the component carriers can be contiguous or non-contiguous witheach other in frequency domain. Bandwidth of the CC can be limited tothe bandwidth of a legacy system for a backward compatibility with thelegacy system. For instance, a legacy 3GPP LTE supports a bandwidth of1.4 MHz, 3 MHz, 5 MHz, 10 MHz, 15 MHz, and 20 MHz and LTE-A may be ableto support a bandwidth bigger than 20 MHz in a manner of using theaforementioned bandwidths supported by LTE only. The bandwidth of eachCC can be individually determined. It is possible to perform anasymmetrical carrier aggregation, which means that the number of DL CCand the number of UL CC is different from each other. DL CC/UL CC linkcan be configured to be fixed in a system or to be semi-static. Forinstance, as shown in FIG. 6 (a), in case that there exist 4 DL CCs and2 UL CCs, it may be possible to configure a DL-UL linkage correspondingto DL CC:UL CC=2:1. Similarly, as shown in FIG. 6 (b), in case thatthere exist 2 DL CCs and 4 UL CCs, it may be possible to configure theDL-UL linkage corresponding to DL CC:UL CC=1:2. Unlike the drawing, itis able to configure a symmetrical carrier aggregation, which means thatthe number of DL CC and the number of UL CC are identical to each other.In this case, it is possible to configure the DL-UL linkagecorresponding to DL CC:UL CC=1:1.

Although a whole bandwidth of a system is configured with N number ofCC, a frequency band capable of being monitored/received by a specificuser equipment can be limited to M (<N) number of CC. Various parametersfor a carrier aggregation can be configured cell-specifically, UEgroup-specifically, or UE-specifically. Meanwhile, control informationcan be configured to be transceived only on a specific channel. Thespecific channel can be called a primary CC (PCC) and the rest of CCscan be called secondary CCs (SCCs).

LTE-A uses a cell concept to manage a radio resource. The cell isdefined as a combination of a DL and UL resource and the UL resource isnot a mandatory element. Hence, a cell can be configured with the DLresource alone or can be configured with the DL resource and the ULresource. In case of supporting the carrier aggregation, a linkagebetween a carrier frequency of the DL resource (or, DL CC) and a carrierfrequency of the UL resource (or, UL CC) can be indicated by systeminformation. A cell operating on a primary frequency (or, PCC) is calleda primary cell (Pcell) and a cell operating on a secondary frequency(or, SCC) is called a secondary cell (Scell).

The Pcell is used for a user equipment to perform an initial connectionestablishment process or a connection re-establishment process. ThePcell may correspond to a cell indicated in the process of a handover.The Scell can be configured after an RRC (radio resource control)connection is established and can be used to provide an additional radioresource. Both the Pcell and the Scell can be commonly called a servingcell. Hence, in case of a user equipment not configured with the carrieraggregation while staying in a state of RRC_CONNECTED or the userequipment not supporting the carrier aggregation, there exists only oneserving cell configured as a Pcell. On the contrary, in case of a userequipment configured with the carrier aggregation and staying in a stateof RRC_CONNECTED, there exists at least one serving cell. And, the Pcelland the whole of the Scells are included in the whole of the servingcell. For the carrier aggregation, after an initial security activationprocess is started, a network may be able to configure at least oneScell for a carrier aggregation supportive user equipment in addition tothe Pcell, which is initially configured in the connection establishmentprocess.

Unlike a legacy LTE system using a single carrier, the carrieraggregation using a plurality of component carriers needs a method ofefficiently managing the component carriers. In order to efficientlymanage the component carriers, the component carriers can be classifiedaccording to a role and property of the component carriers. In thecarrier aggregation, multiple carriers can be divided into a primarycomponent carrier (PCC) and a secondary component carrier (SCC) and thismay correspond to a UE-specific parameter.

The primary component carrier is a component carrier playing a role of acenter of managing the component carriers in case of using a pluralityof component carriers. One primary component carrier is defined for eachof user equipments. The primary component carrier may play a role of acore carrier managing all aggregated component carriers. The secondarycomponent carrier may play a role of providing an additional frequencyresource to provide a higher transfer rate. For instance, a base stationis able to perform an access (RRC) for signaling a user equipment viathe primary cell. In order to provide information necessary for securityand a higher layer, the primary cell can be used as well. In practical,if there exists a single component carrier only, the correspondingcomponent carrier will become a primary component carrier. In this case,the component carrier may be able to play a role identical to that of acarrier of a legacy LTE system.

Among a plurality of component carriers, a base station can assign anactivated component carrier (ACC) to a user equipment. The userequipment is aware of the activated component carrier (ACC) assigned tothe user equipment in advance via a signaling and the like. The userequipment collects responses for a plurality of PDCCHs received from aDL PCell and DL Scells and can transmit the responses on PUCCH via an ULPCell.

In the following description, determination for a user equipment totransmit PUSCH in 3GPP LTE/LTE-A system is described. The followingFormula 1 is a Formula to determine transmit power of a user equipmentin case that PUSCH is transmitted only while PUCCH is not simultaneouslytransmitted in a subframe index i of a serving cell c in a CA supportivesystem.

                                      [Formula  1]${P_{{PUSCH},c}(i)} = {\min {{\begin{Bmatrix}{{P_{{CMAX},c}(i)},} \\{{10{\log_{10}\left( {M_{{PUSCH},e}(i)} \right)}} + {P_{{O\_ PUSCH},c}(j)} + {{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},e}(i)} + {f_{c}(i)}}\end{Bmatrix}\mspace{14mu}\lbrack{dBm}\rbrack}\mspace{664mu}\left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack}}$${P_{{PUSCH},c}(i)} = {\min {\begin{Bmatrix}{{10{\log_{10}\left( {{{\hat{P}}_{{CMAX},c}(i)} - {\underset{PUCCH}{\hat{P}}(i)}} \right)}},} \\{{10{\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{{O\_ PUSCH},c}(i)} + {{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{Bmatrix}\mspace{14mu}\lbrack{dBm}\rbrack}}$

The above-mentioned Formula 2 is a Formula to determine transmit powerof a user equipment in case that PUCCH and PUSCH are simultaneouslytransmitted in a subframe index i of a serving cell c in a CA supportivesystem.

Parameters described in the Formula 1 and the Formula 2, which arenecessary for determining an UL transmit power of a user equipment,relate to the serving cell c.

In this case, P_(CMAX,c)(i) of the Formula 1 indicates transmittablemaximum transmit power of a user equipment in the subframe index i and{circumflex over (P)}_(CMAX,c)(i) of the Formula 2 indicates a linearvalue of P_(CMAX,c)(i). {circumflex over (P)}_(PUCCH)(i) of the Formula2 indicates a linear value of P_(PUCCH)(i). In this case, P_(PUCCH)(i)indicates PUCCH transmit power in the subframe index i.

In the Formula 1, M_(PUSCH,c)(i) is a parameter indicating a bandwidthof PUSCH resource allocation represented by the number of resource blockvalid for the subframe i. This parameter is a value assigned by a basestation. P_(O) _(—) _(PUSCH,c)(j) is a parameter configured by the sumof a cell-specific nominal component P_(O) _(—) _(NOMINAL) _(—)_(PUSCH,c)(j) provided by an upper layer and a UE-specific componentP_(O) _(—) _(UE) _(—) _(PUSCH,c)(j) provided by an upper layer. A basestation informs a user equipment of this value α_(c)(j) indicates apathloss compensation factor. This is a upper layer providingcell-specific parameter transmitted by a base station by 3 bits. αε{0,0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1} where j=0 or 1 and α_(c)(j)=1 wherej=2. A base station informs a user equipment of this value.

Pathloss (PL_(c)) is a DL pathloss (or, signal loss) estimation valuecalculated by a user equipment in dB unit and is represented asPLc=referenceSignalPower−higher layer filteredRSRP. In this case,referenceSignalPower can be informed to a user equipment by a basestation.

f_(c)(i) is a value indicating a current PUSCH power control adjustmentstate for the subframe index i and can be represented by a currentabsolute value or an accumulated value.

Basically, Δ_(TF,c)(i) defined by 3GPP LTE/LTE-A system is configured bya value for one codeword. For a specific codeword index, if K_(S)=1.25,it becomes Δ_(TF,c)(i)=10 log₁₀((2^(BPRE·K) ^(S) −1)·β_(offset)^(PUSCH)). If K_(S)=0, Δ_(TF,c)(i) becomes 0. In this case, the K_(S)may correspond to a UE-specific parameter deltaMCS-Enabled provided to auser equipment via an upper layer by a base station according to acodeword. If K_(S)=0, Δ_(TF,c)(i) becomes 0 and transmit power becomesidentical to each other according to a codeword. Yet, if K_(S)=1.25,transmit power may vary depending on a codeword according to a size (or,a scheduled MCS level) of a transmission information, which isnormalized by an allocated resource of each codeword. In this case, bitsper resource element (BPRE) parameter can be called such a differentname as an MPR and the like. In particular, if K_(s) is not 0,Δ_(TF,c)(i) can be generated based on information quantity per unitresource (e.g., BPRE) according to each codeword.

As mentioned in the foregoing description, basically, Δ_(TF,c)(i)defined by 3GPP LTE/LTE-A system is configured by a value for onecodeword. For a specific codeword index, if K_(S)=1.25, it becomesΔ_(TF,c)(i)=10 log₁₀((2^(BPRE·K)−1)·β_(offset) ^(PUSCH)). If K_(S)=0,Δ_(TF,c)(i) becomes 0. In this case, the K_(s) corresponds to aUE-specific parameter deltaMCS-Enabled provided to a user equipment viaan upper layer by a base station. For a control data transmitted onPUSCH without UL-SCH (uplink shared channel) data, it may be representedas BPRE=O_(CQI)/N_(RE). Otherwise, it may be represented as

$\sum\limits_{r - 0}^{C - 1}{K_{r}/{N_{RE}.}}$

In this case, K_(r) indicates the number of code blocks, C indicates asize of a code block r, O_(CQI) indicates the number of CQI bitincluding CRC bits, and N_(RE) indicates the number of resource elementdetermined by N_(RE)=M_(sc) ^(PUSCH−initial)·N_(symb) ^(PUSCH−initial).In this case, N_(symb) ^(PUSCH−initial) indicates the number of SC-FDMAsymbols carrying PUSCH in an initial PUSCH transmission subframe.

For a control data transmitted on PUSCH without UL-SCH (uplink sharedchannel) data, it may be represented as β_(offset) ^(PUSCH)=β_(offset)^(CQI). Otherwise, it may correspond to 1.

As mentioned earlier, a user equipment has applied 0 or 1.25 as a K_(S)value, which is a UE-specific parameter ‘deltaMCS-Enabled’, in a mannerof receiving the UE-specific parameter via a higher layer signaling.

It is necessary to have an inter-cell interference cancellation(hereinafter abbreviated ICIC) scheme capable of being commonly appliedto an inter-cell interference control technique between a macro cell anda pico/femto cell as well as an inter-cell interference controltechnique between macro cells (or, macro base stations) in a network.The ICIC scheme can also be identically applied to between such lowpower base stations as a pico base station, a femto base station, andthe like. Hence, in a heterogeneous communication system at whichvarious types of base stations exist, it is able to commonly apply notonly a horizontal ICIC scheme for performing an interference controlbetween base stations of an identical type but also a vertical ICICscheme for performing an interference control between base stations ofdifferent types.

When a base station transmits a signal in DL or a user equipmenttransmits a signal in UL, an inter-cell interference control isperformed by the ICIC scheme in a manner of adjusting transmit power fora corresponding scheduled resource. In particular, interferenceaffecting a user equipment situating at a cell boundary in DL or UL canbe reduced by lowering transmit power for a resource assigned to theuser equipment situating at a cell boundary by a neighboring cell. TheICIC scheme using a transmit power control can be performed by aresource block (RB) unit in frequency domain as an example and may beperformed by a subframe unit and the like in time domain as an example.

FIG. 8 is a diagram for an example of an inter-cell interferencesituation.

As a method of efficiently performing an inter-cell interference controltechnique, the present invention assumes a system to which a basic ICICtechnique is applied. As depicted in FIG. 8, in case that a UE 2 820 issituated at a cell boundary, inter-cell interference affecting the UE 2in DL/UL becomes very serious and there may exists a situation that theinter-cell interference should be reduced. Referring to FIG. 8, a cell#1 is interfering a user equipment situating at a cell boundary of acell #2 in DL. On the contrary, the user equipment situating at a cellboundary of the cell #2 is interfering the cell #1 in UL.

In order to solve the above-mentioned situation, base stations 820/830of each cell performs the ICIC scheme for neighboring base stations. Thebase stations 820/830 of each cell can perform the ICIC technique ineither a frequency resource region or a time resource region based onthe aforementioned resource structure. In particular, the interferenceaffecting the neighboring base stations can be mitigated or eliminatedin a manner of defining an interval where a resource is transmitted by alow transmit power in each resource region or an interval where aresource is not transmitted at all and then making the user equipmentsituating at a cell boundary of a neighbor cell receive a service in theinterval.

The ICIC scheme can also be commonly applied to a heterogeneous networkenvironment including various types of base stations as well asoperations between the aforementioned macro base stations. For instance,the heterogeneous network means a system environment where such lowpower base stations as a pico cell and a femto cell coexist besides themacro base station.

A specific time unit interval can be used as a blanking interval where asignal is not transmitted. In this case, following description isexplained on the basis of a subframe as an example of the specific timeunit. Each base station configures a specific subframe as a blankingsubframe in order not to interfere a neighboring cell. Currently, 3GPPLTE-A standard regulates a non-transmitted subframe to perform aninterference control in time domain with a name of an almost blankingsubframe (ABS).

FIG. 9 is a diagram for an example of an inter-cell interferencesituation in a heterogeneous network environment.

A heterogeneous system (or a network) means a system configured by usingvarious types of base stations. In a heterogeneous network, a totalsystem capacity can be maximized by managing a plurality of low powerpico base stations and femto base stations of a small coverage togetherwith a high power macro base station of a wide coverage. The pico basestation is mainly installed in a hot zone requiring many data trafficsand the femto base station supports such a service of a very smallcoverage as an individual home.

FIG. 9 shows an example of a heterogeneous network (system)configuration. When an identical carrier is simultaneously managedbetween base stations of different types overlaid in the heterogeneousnetwork, interference occurs. In particular, an interference situationmay occur between a macro base station and a pico base station/femtobase station as well as between macro base stations. And, theinterference situation can occur between a pico base station and a femtobase station as well. Hence, it is necessary to have an inter-cellinterference control scheme. Hence, the ICIC scheme is used not only forcontrolling interference between macro base stations, but also forcontrolling interference between a macro base station and a pico/femtobase station. In this case, all techniques of the ICIC scheme used tocontrol interference between macro base stations can be identicallyapplied and an additional scheme may be used to optimize a performance.Moreover, if there exists a link capable of communicating between basestations although types of the base stations are different from eachother, a dynamic ICIC scheme of an identical type can be applied to thebase stations.

In a heterogeneous communication system at which various types of basestations exist, the present invention is able to commonly apply not onlya horizontal ICIC scheme for performing an interference control betweenbase stations of an identical type but also a vertical ICIC scheme forperforming an interference control between base stations of differenttypes.

As mentioned in the foregoing description, the ICIC scheme can beapplied to a time domain and a frequency domain. A core part of the ICICscheme is to determine a transmit power pattern in a time resourceregion or a frequency resource region. In particular, it is necessary todetermine a frequency resource or a time resource to be transmitted witha high transmit power, an interval to be transmitted with low transmitpower, or an interval to be defined as a non-transmitted interval.

A transmit power pattern or a pattern of a non-transmitted interval foran interference control can be variously configured according to asystem regulation. A scheme of managing an interference control resourceregion and a transmit power pattern in a manner of being fixed accordingto a promise predetermined between base stations is called a static ICICscheme in the present specification. And, a scheme of managing theinterference control resource region and the transmit power pattern in amanner of changing according to an operation environment is called adynamic ICIC scheme in the present specification.

In order to perform the dynamic ICIC scheme, it is necessary to exchangepattern information of transmit power according to resources betweenbase stations and share the pattern information. According to 3GPP LTEsystem regulation, pattern information of transmit power according tofrequency resources in DL is exchanged by such a message as a relativenarrow transmit power (RNTP) of a bitmap form and pattern information oftransmit power according to frequency resources in UL is exchanged bysuch a message as a high interference indicator (HII). In case of UL,since a severely interfering resource corresponds to a resource used bya user equipment situating at a cell boundary, information on theresource allocated to the user equipment situating at the cell boundaryis exchanged by an HII message of a bitmap form. According to 3GPP LTE-Asystem regulation, ABS pattern information in time domain is exchangedwith each other between base stations.

According to a UL power control to which a fractional pathlosscompensation method is applied thereto, a pathloss compensation factor,which is one of the configuration elements of the UL power control, canbe cell-specifically configured by an upper layer signaling. Since thepathloss compensation factor statically/semi-statically changes, if auser equipment moves to a cell of an isolated form or a pico cell/femtocell/RRH (remote wireless device playing a role of a very small basestation), which are not acting as sources of interference to aneighboring cell, from the inside or outside of a macro cell, it isdifficult to directly apply a full pathloss compensation form or anappropriate parameter for transit power of the user equipment.

The present invention is described on the basis of an isolated cellscenario, this is just an example. The present invention can be appliedto a cell where transmit power of a user equipment within the cell doesnot affect a neighboring cell as a source of interference. Inparticular, an isolated cell described in the present specification mayindicate a cell not interfering a neighboring cell, although thecorresponding cell transmits a signal.

In a system where a radio resource is shared since a pico cell/femtocell/RRH coexist within a macro cell, a co-channel interference problemoccurs depending on a method and becomes a major factor of systemperformance degradation. In order to solve the co-channel interferenceproblem, when a pico UE performs a transmission in a UL subframe of themacro cell, if the UL subframe of the macro cell corresponds to analmost blanking subframe (ABS), a pathloss compensation factor among ULpower control elements of the pico UE/femto UE/RRH UE is set to 1, avalue identical to the macro cell, or a value different from the macrocell to determine transmit power of a UL data channel (PUSCH) and thepico UE transmits UL data using the determined transmit power. 3GPPLTE-A system standard regulates the almost blanking subframe (ABS) as anon-transmitted subframe in time domain to perform an interferencecontrol. ABS pattern information in time domain is exchanged with eachother between base stations.

A method of calculating UL transmit power for a macro UE can berepresented by Formula 3 as follows.

                                      [Formula  3]${P_{{PUSCH},c}(i)} = {\min {\begin{Bmatrix}{{P_{{CMAX},c}(i)},} \\{{10{\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{{O\_ PUSCH},c}(j)} + {{\alpha_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{Bmatrix}\mspace{14mu}\lbrack{dBm}\rbrack}}$

Each transmit power parameter defined by Formula 3 has a meaningidentical to that of the parameters explained in the Formula 1 and theFormula 2.

While using α_(c)(j) in a manner of setting with a value less than 1, ifa user equipment transmits data in an isolated pico cell, UL transmitpower can be determined by setting α_(c)(j) with 1 or a differentsetting value. Or, it may be able to apply a value set by adding j valueof α_(c)(j). According to a related art, ‘j’ corresponds to ‘0’, ‘1’, or‘2’. ‘0’ is used for a semi-persistent grant, ‘1’ is used for a dynamicscheduled grant, and ‘2’ is used for a random access response grant. Inthis case, if ‘j=3’ is additionally set and data is transmitted in acorresponding pico cell/RRH/femto cell, UL transmit power for UL datachannel transmission is determined by using the α_(c)(j) value.

In the Formula 3, P_(O) _(—) _(PUSCH,c)(j) can be configured with aUE-specific value and a cell-specific value. If a UE moves from a macrocell to such an isolated cell as a pico cell/RRH/femto cell, theUE-specific value of P_(O) _(—) _(PUSCH,c)(j) different from that of themacro cell is applied. The above-mentioned two elements are informed tothe UE by a base station via an upper layer signaling. Hence, if the UEmoves to a pico cell/RRH/femto cell, the corresponding picocell/RRH/femto cell commonly or UE-specifically informs the UE of thetwo elements in order for the UE to adaptively use the two elements likethe α_(c)(j). Both of the two values or one of them is informed as avalue to be used by the pico cell/RRH/femto cell or an offset value tobe added is informed.

Following Formula 4 is a Formula for explaining a different embodimentof a method of determining PUSCH transmit power in consideration of apathloss compensation factor.

                                      [Formula  4]${P_{{PUSCH},c}(i)} = {\min \left\{ \begin{matrix}{{P_{{CMAX},c}(i)},} \\{{10{\log_{10}\left( {M_{{PUSCH},c}(i)} \right)}} + {P_{{O\_ PUSCH},c}(j)} + {{\alpha_{c}(j)} \cdot {\beta_{c}(j)} \cdot {PL}_{c}} + {\Delta_{{TF},c}(i)} + {f_{c}(i)}}\end{matrix} \right\}}$

In the Formula 4, a pathloss compensation factor can be applied in amanner of being configured by α_(c)(j)·β_(c)(j) form. α_(c)(j) is aparameter value used for a macro cell and β_(c)(j) becomes a parameterfor a pico cell/RRH/femto cell. For instance, when the α_(c)(j)corresponds to 1 in a macro cell, the β_(c)(j) may correspond to aparameter for the pico cell/RRH/femto cell. Unlike the Formula 4, thepathloss compensation factor can be represented as the β_(c)(j) formtaken into account a α_(c)(j) value instead of being represented as theα_(c)(j)·β_(c)(j) form.

Since transmit power of a base station or a user equipment in anisolated cell can be excluded from working as interference to a basestation signal or a user equipment signal of a neighboring cell,performance of a pico cell/RRH/femto cell can be enhanced in a manner ofperforming a full power loss compensation and then sufficientlyassigning necessary transmit power.

In FIG. 9, configuration of a macro cell and a pico cell is brieflydescribed. The macro cell and the pico cell can use one radio resource.Moreover, the macro cell and the pico cell can use one or more radioresources. In the following description, assume that the macro cell andthe pico cell use one radio resource.

FIG. 10 is an exemplary diagram for explaining a downlink eICIC solutionin a configuration depicted in FIG. 9.

Referring to FIG. 10, as a part of an enhanced inter-cell interferencecoordination (eICIC), there is a method of using a time divisionmultiplexing (TDM) of cell-layers in DL as an example of a non-CA(carrier aggregation) based solution as depicted in FIG. 10. This is amethod of not allocating a part or the whole of resource in a mannerthat a base station of a macro cell configures a DL subframe of themacro cell as an almost blanking subframe (ABS). By doing this, a DLsignal of the macro cell, which works as a big source of interference toa DL signal of a pico cell, is mitigated, thereby enhancing a receptionperformance of a user equipment in the pico cell.

In the same vein, the macro cell and the pico cell can use a radioresource by the TDM scheme as depicted in FIG. 11 in relation to a ULtransmission interval.

FIG. 11 is an exemplary diagram for explaining an uplink eICIC solutionin a configuration depicted in FIG. 9.

In case that a user equipment of a macro cell performs a transmission inthe vicinity of a pico cell in a UL transmission interval, it may causea significant interference to a UE signal of the pico cell. In order tomitigate or eliminate the interference for the pico cell, an ABS can beapplied to the UL transmission interval of the macro cell as depicted inFIG. 11. Referring to FIG. 11, the macro cell and the pico cell canschedule UEs in each cell to transmit a signal in an UL intervaldifferent from each other. In particular, inter-cell interference can beeliminated or mitigated in a manner that a UE of the macro cell and a UEof the pico cell transmit a UL signal in a UL transmission intervaldifferent from each other. Based on this, a method of using a part orthe whole of resources in the macro cell and the pico cell can beapplied in various ways. As depicted in FIG. 11, the macro cell sets aUL transmission interval to an ABS in the UL transmission interval ofpico cell UEs. Similarly, the pico cell sets a UL transmission intervalto an ABS in the UL transmission interval of a macro cell UE.

FIG. 12 is a different exemplary diagram for explaining an uplink eICICsolution in a configuration depicted in FIG. 9.

While a form of the UL transmission interval of the macro cell depictedin FIG. 11 is maintained as it is,

the UL transmission interval of the pico cell becomes a form of beingused all UL transmission intervals. It is also possible to apply apattern indicating whether a part of resource is used in the UL intervalused by both the macro cell and the pico cell. For instance, it is amethod that a macro cell UE uses PUSCH region and a pico cell UE usesPUCCH only.

In FIG. 12, the pico cell UEs can apply a full pathloss compensationfactor in the ABS interval in case of determining an UL transmit power.

Although a single pico cell is depicted in FIG. 9, there may exist aplurality of pico cells. A method of applying a configuration value forpathloss compensation may vary according to a type of a pico cell. Forinstance, if a type of a cell corresponds to an isolated cell, fullpathloss compensation is applied. Otherwise, fractional pathlosscompensation is applied. A type relation of a cell can be summarized inTable 2 as follows.

TABLE 2 Macro cell Pico cell Case 1 Isolated cell Non-Isolated cell typeCase 2 Isolated cell Isolated cell Case 3 Non-Isolated cell typeIsolated cell Case 4 Non-Isolated cell type Non-Isolated cell type

If a macro cell or a pico cell corresponds to an isolated cell, fullpathloss compensation is basically applied. Yet, in case of using aresource as depicted in FIG. 11, there is no problem. Yet, in case ofusing a resource as depicted in FIG. 12, it may be more efficient andhelpful to control quantity of interference given to the pico cell byapplying the fractional pathloss compensation instead of applying thefull pathloss compensation.

A method of determining a pathloss compensation factor for a UE transmitpower in a macro cell may be different from a method of applying atransmit power according to an eICIC (a method of using a resource). Apattern using a different value with a subframe level or a symbol levelfor pathloss compensations (or, each of power control parameters) can bedesignated in advance and used according to a resource allocationpattern for the eICIC. The pattern can be cell-specifically(pico-cell/RRH/femto cell), cell-commonly, or UE-specifically used. Eachcorresponding cell can inform UEs of information on the pathlosscompensation according to the resource allocation pattern and the likeby signaling with a broadcast type, a unicast type, and the like. Or,the value can be informed to the UE cell-specifically or UE-specificallyaccording to the macro cell. Or, in accordance with a predeterminedsubframe set or a subframe pattern, values to be applied can beconfigured by a set. It is also able to configure according to asubframe or a symbol level. As an example, at least one or more can beused in a manner of being configured by a form of ‘if SFN mod A=B, αvalue (or, a UE-specific value) is C’. In this case, the SFN is a valueindicating a subframe number (or, an index). In this case, A, B, and Cmay correspond to predetermined fixed values and can be transmitted to aUE via an upper layer/dynamic grant with a semi-static/dynamic value bya cell.

When a UE moves to an isolated pico cell from a macro cell, if the picocell type corresponds to an isolated cell, the UE can set a pathlosscompensation factor to 1 (or a designated value). The macro cell mayinform one, a part, or all pico cells of information on the pico celltype and the corresponding pico cell can inform the pico cell type aswell. In this case, the information on the pico cell type can beinformed by a broadcast message type, a unicast message type, and thelike.

Meanwhile, when a UE moves to an isolated pico cell from a macro cell, acorresponding pico cell can newly inform of a pathloss compensationfactor or the macro cell can inform of the pathloss compensation factoraccording to a pico cell. In this case, the information on the pico celltype can be informed by a broadcast message type, a unicast messagetype, and the like.

According to the above-mentioned embodiments of the present invention,performance of a pico cell, an RRH, a femto cell can be maximized in asituation that an eICIC is taken into consideration.

The above-described embodiments may correspond to combinations ofelements and features of the present invention in prescribed forms. And,it may be able to consider that the respective elements or features maybe selective unless they are explicitly mentioned. Each of the elementsor features may be implemented in a form failing to be combined withother elements or features. Moreover, it may be able to implement anembodiment of the present invention by combining elements and/orfeatures together in part. A sequence of operations explained for eachembodiment of the present invention may be modified. Some configurationsor features of one embodiment may be included in another embodiment orcan be substituted for corresponding configurations or features ofanother embodiment. And, it is apparently understandable that a newembodiment may be configured by combining claims failing to haverelation of explicit citation in the appended claims together or may beincluded as new claims by amendment after filing an application.

While the present invention has been described and illustrated hereinwith reference to the preferred embodiments thereof, it will be apparentto those skilled in the art that various modifications and variationscan be made therein without departing from the spirit and scope of theinvention. Thus, it is intended that the present invention covers themodifications and variations of this invention that come within thescope of the appended claims and their equivalents.

INDUSTRIAL APPLICABILITY

Accordingly, a method of determining an uplink transmit power in anetwork including a plurality of cells and an apparatus therefor areindustrially applicable to various mobile communication systemsincluding 3GPP LTE, LTE-A system, and the like.

What is claimed is:
 1. A method of determining an uplink transmit powerby a user equipment in a network including a plurality of cells, themethod comprising: receiving information containing a pathlosscompensation factor value set for each of the plurality of the cells;determining an uplink transmit power using a pathloss compensationfactor value corresponding to a cell at which the user equipment iscurrently positioned among the plurality of the cells; and transmittingan uplink signal using the determined transmit power.
 2. The method ofclaim 1, wherein the plurality of the cells comprise a heterogeneouscell and wherein the set pathloss compensation factor value is differentfrom each other between the heterogeneous cells.
 3. The method of claim1, wherein the pathloss compensation factor value set for each of thecells is configured in accordance with the cells based on a resourceallocation pattern for each of the cells.
 4. The method of claim 3,wherein the pathloss compensation factor value set for each of the cellsis configured with a specific time unit in each of the cells.
 5. Themethod of claim 4, wherein the specific time unit comprises a frame, asubframe, or a symbol unit.
 6. The method of claim 1, wherein the uplinktransmit power corresponds to a transmit power for PUSCH (physicaluplink shared channel) transmission.
 7. The method of claim 3, whereinthe pathloss compensation factor value set for each of each of theplurality of the cells is set further based on whether each of the cellscorresponds to an isolated cell.
 8. The method of claim 3, furthercomprising: receiving information on the resource allocation pattern foreach of the cells, wherein the resource allocation pattern for each ofthe cells comprises at least one an ABS (almost blanking subframe)assignment pattern information for each of the cells, information onPUSCH (physical uplink shared channel) transmission resource for each ofthe cells, or information on PUCCH transmission resource information foreach of the cells.
 9. A user equipment for determining an uplinktransmit power in a network including a plurality of cells, the userequipment comprising: a receiver configured to receive informationcontaining a pathloss compensation factor value set per each of theplurality of the cells; a processor configured to determine a uplinktransmit power using the pathloss compensation factor valuecorresponding to a cell at which the user equipment is currentlypositioned among each of the plurality of the cells; and a transmitterconfigured to transmit an uplink signal using the determined transmitpower.
 10. The user equipment of claim 9, wherein the pathlosscompensation factor value set for each of the cells is configured inaccordance with the cells based on a resource allocation pattern foreach of the cells.
 11. The user equipment of claim 10, wherein thereceiver is configured to further receive information on the resourceallocation pattern for each of the cells, wherein the resourceallocation pattern for each of the cells comprises at least one an ABS(almost blanking subframe) assignment pattern information according tothe cells, information on PUSCH (physical uplink shared channel)transmission resource for each of the cells, or information on PUCCHtransmission resource for each of the cells.